Exposure structure and exposure equipment

Abstract

This invention relates to the field of holographic lithography technology, specifically to exposure structures and exposure equipment. By limiting the theoretical imaging distance in the exposure structure to be greater than the thickness of the transparent mask substrate but less than the sum of the maximum thickness of the immersion droplet and the thickness of the transparent mask substrate when the exposure beam passes through the transparent mask substrate and is completely imaged in the immersion liquid, it is ensured that the exposure beam can completely image the interior of the immersion droplet after passing through it, thereby ensuring that the exposure beam can be completely imaged on the wafer substrate, which can greatly improve the lithography quality. At the same time, by calculating and setting a smaller imaging distance, and using surface tension to form the immersion droplet without completely immersing the transparent mask substrate or wafer substrate in the immersion liquid, a smaller imaging structure size and less immersion liquid are achieved, which facilitates the cleaning of the wafer substrate and transparent mask substrate after lithography.

Description

Technical Field

[0001] This invention relates to the field of holographic lithography technology, specifically to exposure structures and exposure equipment. Background Technology

[0002] Laser holographic lithography is a promising lithography technology. Its basic principle is diffraction imaging. A beam of light illuminates a holographic mask and diffracts on microstructures arranged in a certain pattern. These diffractions are eventually superimposed on a silicon wafer to obtain the desired pattern.

[0003] In traditional photolithography, to address the challenge of increasingly smaller feature sizes, besides reducing the laser wavelength, immersion lithography is often used to improve resolution. Immersion lithography replaces the air medium between the projection lens and the silicon wafer in traditional photolithography with water, which has a higher refractive index, thereby increasing the numerical aperture and further improving the lithography machine's resolution. In holographic lithography, when the photolithography resolution reaches its limit, immersion in a liquid can be used to further enhance the resolution.

[0004] In existing holographic lithography apparatuses, to achieve smaller lithographic feature sizes, the optical path for generating holographic images at a set distance is typically immersed in water. Simultaneously, amplitude diffraction elements, phase diffraction elements, and the substrate to be etched with photoresist are all submerged in water, performing holographic lithography underwater. However, due to the small gaps between the micro- and nano-structures on the mask, the presence of air pressure and surface tension when the mask is submerged creates tiny gaps between the water and the micro- and nano-structures, resulting in poor projection quality of the laser beam after passing through the mask, thus affecting the lithography quality. Furthermore, because the optical path distance is relatively large, immersing the entire optical path in water leads to a large water consumption, resulting in a larger image structure size for the entire system and difficulties in water treatment between the mask and the substrate when removing the substrate after lithography. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the existing holographic lithography system that the lithographic structure on the mask cannot be completely immersed in water, which affects the lithography quality, thereby providing an exposure structure and exposure equipment.

[0006] To solve the above-mentioned technical problems, the present invention provides an exposure structure, comprising:

[0007] A wafer substrate, on one side of which is provided a photoresist layer;

[0008] A transparent mask substrate on which a holographic pattern is disposed, the holographic pattern being disposed on the side of the transparent mask substrate facing away from the wafer substrate, and the side of the wafer substrate with a photoresist layer facing the transparent mask substrate;

[0009] An immersion droplet is positioned between a transparent mask substrate and a wafer substrate. The immersion droplet is adsorbed between the transparent mask substrate and the wafer substrate by surface tension, and both the transparent mask substrate and the wafer substrate are in contact with the immersion droplet.

[0010] When the exposure beam is fully imaged in the immersion liquid after passing through the transparent mask substrate, the theoretical imaging distance is greater than the thickness of the transparent mask substrate and less than the sum of the maximum thickness of the droplet and the thickness of the transparent mask substrate.

[0011] Optionally, when the exposure beam completely images the image in the immersion liquid after passing through the transparent mask substrate, the theoretical imaging distance z is calculated according to the following formula:

[0012] z = (z0 - z1 / n1)n2

[0013] Where z0 is the fully air imaging distance set by the transparent mask substrate, n1 is the refractive index of the transparent mask substrate, and n2 is the refractive index of the immersed droplet.

[0014] Optionally, a hydrophilic layer is provided on the surface of the photoresist layer.

[0015] Optionally, a hydrophobic structure layer is provided on the transparent mask substrate, and the hydrophobic structure layer and the holographic pattern are respectively provided on two opposite sides of the transparent mask substrate.

[0016] Optionally, a limiting groove is provided on the side of the transparent mask substrate facing away from the holographic pattern, and the limiting groove is provided in correspondence with the holographic pattern.

[0017] Optionally, a flow channel is also provided on the transparent mask substrate. One end of the flow channel is connected to the limiting groove, and the other end extends to the edge of the transparent mask substrate and connects to the outside. The flow channel is connected to a fluid drive pump.

[0018] Optionally, the volume of the immersed droplet is the product of the bottom area of ​​the limiting groove and the theoretical distance.

[0019] Optionally, a photonic crystal layer is provided on the bottom surface of the limiting groove.

[0020] The present invention also provides another exposure structure, comprising:

[0021] A wafer substrate, on one side of which is provided a photoresist layer;

[0022] A transparent mask substrate on which a holographic pattern is disposed, wherein the holographic pattern is disposed on the side of the transparent mask substrate opposite to the wafer substrate, and the side of the wafer substrate on which the photoresist layer is disposed faces the transparent mask substrate;

[0023] An immersion droplet is adapted to be disposed between the transparent mask substrate and the wafer substrate. The immersion droplet is adapted to be adsorbed onto the surface of the wafer substrate by surface tension. The immersion droplet is disposed separately from the transparent mask substrate.

[0024] The present invention also provides an exposure device having the exposure structure described herein, and further including an exposure light source, an illumination optical path, a reflector and a mask loading stage. A transparent mask substrate is mounted on the mask loading stage, and the light beam emitted by the exposure light source passes through the illumination optical path for optical path adjustment and is reflected by the reflector before irradiating the transparent mask substrate.

[0025] The technical solution of this invention has the following advantages:

[0026] 1. The exposure structure provided by this invention, when patterning on a wafer substrate, involves an exposure beam first passing through a holographic pattern on a transparent mask substrate to form patterned optical information. The beam then passes through the transparent mask substrate and enters an immersion droplet. After being reduced in size by the immersion droplet, it illuminates the photoresist layer of the wafer substrate, completing the photolithography of the wafer substrate. By placing an immersion droplet between the transparent mask substrate and the wafer substrate, and placing the holographic pattern on the side of the transparent mask substrate facing away from the wafer substrate, the exposure beam first passes through the holographic pattern and then is reduced in size by the immersion droplet to form an image. The immersion droplet can completely immerse the surface of either the transparent mask substrate or the wafer substrate. However, due to the different imaging parameters of different transparent mask substrates, the imaging position of the exposure beam after passing through the transparent mask substrate may be inside the transparent mask substrate or located on the back side of the wafer body, resulting in the photoresist layer of the wafer substrate not being etched, thus preventing immersion photolithography of the wafer substrate. By limiting the theoretical imaging distance for complete imaging of light through the transparent mask substrate in the immersion liquid to a value greater than the thickness of the transparent mask substrate but less than the sum of the maximum thickness of the immersion droplet and the thickness of the transparent mask substrate, the exposure beam can be completely imaged inside the immersion droplet after passing through it. By adjusting the position of the wafer substrate, it can be ensured that the exposure beam can be completely imaged on the wafer substrate after passing through the immersion droplet, which can greatly improve the lithography quality. At the same time, by calculating and setting a smaller imaging distance, the immersion droplet is formed using surface tension without completely immersing the transparent mask substrate or wafer substrate in the immersion liquid. This achieves a smaller imaging structure size and less immersion liquid usage, which facilitates the cleaning of the wafer substrate and transparent mask substrate after lithography.

[0027] 2. The exposure structure provided by the present invention has a hydrophilic layer on the surface of the photoresist layer to increase the surface tension between the photoresist layer and the immersed droplet, thereby increasing the maximum thickness of the immersed liquid on the surface of the photoresist layer, thereby increasing the imaging distance, increasing the distance at which holographic pattern imaging can be received within the immersed droplet, and reducing the assembly accuracy required for normal operation of the device.

[0028] 3. The exposure structure provided by this invention includes a hydrophobic structural layer on a transparent mask substrate, with the hydrophobic structural layer and the holographic pattern respectively disposed on opposite sides of the transparent mask substrate. By adding the hydrophobic structural layer, the adhesion between the transparent mask body and the immersed droplet is increased. Hydrophobic high-adhesion and hydrophobic low-adhesion surfaces can be achieved by modifying the surface micro / nano structure. This allows for both high adhesion before immersion to increase the liquid thickness and hydrophobicity after immersion, thereby protecting the transparent mask substrate.

[0029] 4. The exposure structure provided by this invention has a limiting groove on the side of the transparent mask substrate facing away from the holographic pattern, and the limiting groove is correspondingly set to the holographic pattern. By setting the limiting groove corresponding to the holographic pattern, the position of the immersed droplet is restricted, so that the immersed droplet can accurately flow to the area corresponding to the holographic pattern, thereby improving the accuracy of the immersed droplet position and improving the photolithography quality of the exposure structure.

[0030] 5. The exposure structure provided by this invention further includes a drainage channel on the transparent mask substrate. One end of the drainage channel is connected to a limiting groove, and the other end extends to the edge of the transparent mask substrate and connects to the outside. A fluid-driven pump is connected to the drainage channel. The purpose of drainage is achieved by etching the drainage channel, and then the residual liquid is extracted by the fluid-driven pump to achieve the purpose of cleaning the transparent mask body after photolithography.

[0031] 6. The exposure structure provided by the present invention has a photonic crystal layer disposed on the bottom surface of the limiting groove. By etching the photonic crystal layer in the limiting groove corresponding to the holographic pattern area, a light field confinement of a specific wavelength is achieved on the photonic crystal structure, thereby improving the utilization rate of the exposure beam energy. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the exposure apparatus provided in the first embodiment of the present invention, wherein the arrow indicates the propagation direction of the exposure beam.

[0034] Figure 2 This is a schematic diagram illustrating how a droplet remains on a solid surface under the action of surface tension, as provided in an embodiment of the present invention.

[0035] Figure 3This is a schematic diagram illustrating the gradual increase in droplet volume as it remains on a solid surface under the influence of surface tension, according to an embodiment of the present invention.

[0036] Figure 4 This is a force analysis diagram of a droplet remaining on a solid surface under the action of surface tension, provided in an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram illustrating the change of the hydrophobic structure layer from hydrophobic to being submerged by droplets in an embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of the limiting groove provided in an embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of the structure of the photonic crystal layer provided in an embodiment of the present invention.

[0040] Figure 8 This is a schematic diagram of an exposure device provided in another embodiment of the present invention, wherein the arrow indicates the propagation direction of the exposure beam.

[0041] Explanation of reference numerals in the attached figures: 1. Exposure light source; 2. Illumination optical path; 3. Reflector; 4. Mask loading stage; 5. Transparent mask substrate; 6. Immersed droplet; 7. Exposure stage; 8. Limiting groove; 9. Drainage channel; 10. Fluid-driven pump; 11. Hydrophobic structure layer; 12. Photonic crystal layer. Detailed Implementation

[0042] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] Figure 1 The diagram illustrates an exposure apparatus provided in this embodiment, comprising an exposure structure consisting of a wafer substrate, a transparent mask substrate 5, and an immersion droplet. It also includes a laser as an exposure light source 1, an illumination optical path 2, a reflector 3, and a mask mounting stage 4. The wafer substrate is fixedly mounted on an exposure stage 7. In some other embodiments, the exposure light source 1 can also be a laser light source, an extreme ultraviolet light source, an X-ray light source, or other light source capable of exposing the wafer.

[0047] The transparent mask substrate 5 is fixedly mounted on the mask loading stage 4. The laser beam emitted by the laser passes through the illumination optical path 2 for optical path adjustment and is reflected by the reflector 3 before irradiating the transparent mask substrate 5. After carrying holographic pattern information, it passes through the immersion droplet 6 and irradiates the wafer substrate to perform photolithography on the wafer substrate.

[0048] A photoresist layer is formed on the side of the wafer substrate that is irradiated by the laser. A holographic pattern is formed on the transparent mask substrate 5, with the holographic pattern on the side of the transparent mask substrate 5 facing away from the wafer substrate. The side of the wafer substrate with the photoresist layer faces the transparent mask substrate 5. An immersion droplet 6 is placed between the transparent mask substrate 5 and the wafer substrate, and the immersion droplet 6 is adsorbed onto the surface of the transparent mask substrate 5 and the surface of the wafer substrate by surface tension. In this embodiment, the exposure structure adopts an upright structure, with the transparent mask substrate 5 located below the wafer substrate, and both the transparent mask substrate 5 and the wafer substrate in contact with the immersion droplet 6. It should be noted that in this embodiment, the transparent mask substrate 5 is a quartz glass substrate. Except for the holographic pattern area, other parts of the transparent mask substrate 5 need to be shielded by a metal film. The metal film is placed on the side of the transparent mask substrate 5 with the holographic pattern to block stray light, allowing only the holographic pattern area to transmit light. On the side of the transparent mask substrate 5 without the holographic pattern, the entire surface is a smooth quartz substrate surface.

[0049] To ensure that the laser beam can project the image of the holographic pattern onto the wafer substrate, when preparing the transparent mask substrate 5, the theoretical distance that the laser travels in the immersion liquid when it passes through the transparent mask substrate 5 and forms a complete image is limited is not greater than the maximum thickness of the droplet on the surface of the transparent mask substrate 5.

[0050] The beam is emitted by a laser, and after the wavefront and beam radius are adjusted by the illumination optical path 2, it is reflected by the reflector 3 and irradiated onto the transparent mask substrate 5 on the mask loading stage. By dropping immersion droplets 6 onto the transparent mask substrate 5, the pattern in the beam shrinks as it passes through the immersion droplets 6, and finally the designed integrated circuit pattern is obtained on the wafer substrate on the exposure stage 7.

[0051] In the exposure structure, after the laser beam is shaped and collimated into a plane wave through the illumination optical path 2, it is reflected by the reflector 3 onto the vertical mask loading stage. The transparent mask substrate 5 is flipped downward to separate the immersion droplet 6 from the holographic pattern that serves as the mask micro-nano structure. Then, water is dropped on the back of the transparent mask substrate 5, and the immersion is achieved by the surface tension of the water on the quartz substrate. Finally, the integrated circuit pattern formed by the transparent mask substrate 5 forms a holographic image in the set immersion area. The wafer substrate coated with photoresist on the exposure stage 7 is then exposed to obtain the designed integrated circuit pattern.

[0052] In this embodiment, the transparent mask substrate 5 is flipped and immersed so that the holographic pattern faces downwards, achieving complete immersion without damaging the micro / nano structure of the holographic pattern. The back-side immersion method also makes it easier to clean the liquid from the surface of the transparent mask substrate 5. By calculating and setting a smaller imaging distance and utilizing the surface tension of the liquid on the transparent mask substrate 5, a smaller imaging structure size and less water consumption are achieved.

[0053] The advantages of the technical solution provided in this embodiment are explained below with reference to theoretical derivation and accompanying drawings:

[0054] Consider the following scenario: water is slowly poured onto a perfectly smooth substrate. Assuming that the water remains a single, continuous droplet as its volume increases, the relationship between the droplet's thickness and volume is analyzed below:

[0055] When the liquid volume is very small, the droplet on the solid surface is as follows: Figure 2 As shown, the height e of the droplet at this time is:

[0056]

[0057] In equation (1), r is the radius of the droplet and θ is the contact angle between the liquid and the solid surface.

[0058] The volume V of the droplet at this time is:

[0059]

[0060] As the liquid volume increases, the droplet on the solid surface changes as follows: Figure 3 As shown, when the droplet volume is very small, surface tension dominates, and gravity is negligible, so the droplet can maintain its spherical shape. However, when the droplet size exceeds the capillary length (approximately 2.71 mm), gravity begins to dominate. The droplet flattens under the influence of gravity. Through mechanical analysis, we can derive the relationship between the thickness *e* of this flattened droplet and the contact angle θ with the solid surface. E The relationship is as follows. Force analysis is performed on a portion of the droplet, establishing its force equilibrium equations in the horizontal direction. A force diagram is shown below. Figure 4 As shown: From Figure 4 It can be seen that this droplet is subjected to two forces: surface tension f1 and the hydrostatic pressure P of the liquid. The surface tension f1 is:

[0061] f1=γ SO -(γ+γ SL (3)

[0062] In equation (3) γ SO γ is the force pulling the droplet outward from its edge, and γ is the force pulling the droplet from its center towards its center. SL This is the pulling force that causes the droplet to converge from the bottom center towards the center.

[0063] The hydrostatic pressure P of the liquid acts over the entire height of the liquid film. By integrating over the entire thickness of the liquid film, we can obtain:

[0064]

[0065] In equation (4), ρ is the droplet density, g is the gravitational constant, and z is the angle between any position on the droplet surface and the horizontal direction.

[0066] The force balance equation for a droplet per unit length is:

[0067]

[0068] According to Young's equation, the surface tension above can be converted into a formula expressing the contact angle:

[0069] γ SO -(γcosθ E +γ SL )=0 (6)

[0070] Combining the above equations, we can conclude that:

[0071]

[0072] The volume of the droplet at this time is:

[0073]

[0074] In equation (8), S is the bottom area of ​​the droplet.

[0075] The above mechanical analysis shows that the thickness and volume of a large droplet are independent of the solid surface wettability. Based on equation (7), under constant surface tension and contact angle, the maximum thickness a droplet can achieve on the substrate surface can be calculated as follows:

[0076] The following is a theoretical calculation of the imaging position after the laser beam illuminates the holographic pattern, passes through the transparent mask substrate 5, and is immersed in the droplet 6:

[0077] Parallel light is incident perpendicularly onto a transparent mask. The holographic pattern micro / nano structure on the transparent mask is a pinhole structure. Consider the complex amplitude field of single-hole diffraction:

[0078]

[0079] In equation (9), U represents the complex diffraction amplitude of a single square aperture, centered at the origin, L represents the size of the square aperture, and λ represents the wavelength of light.

[0080] If the holographic pattern is backed by a transparent mask body medium with a refractive index of n, then the z-axis is located at... g Complex amplitude U at the location g for

[0081]

[0082] Then propagate z in the submerged droplet 6 a Complex amplitude U of distance a for:

[0083]

[0084] It can be seen that if z a Defined as Then U a with U g Only phase factor (in the sense that r is expanded to the second order and y / r and x / r are expanded to the first order).

[0085] Therefore, assuming that the original beam propagated a distance z in the air after being diffracted by the holographic pattern, and the beam now propagates a distance z1 in the transparent mask substrate 5, the final imaging distance is around z1+z-z1 / n.

[0086] Assuming the fully air imaging distance of the transparent mask substrate 5 is set to z0 and the thickness of the transparent mask substrate 5 is z1, the laser beam will eventually pass through the holographic pattern on the transparent mask substrate 5 and then be imaged in the immersed droplet 6. The theoretical distance for the laser beam imaging is z = (z0 - z1 / n1)n2, where n1 is the refractive index of the transparent mask substrate 5 and n2 is the refractive index of the immersed droplet 6.

[0087] When fabricating the transparent mask substrate 5, it should be ensured that the laser beam, after passing through the holographic pattern diffraction and the transparent mask substrate 5, images in the immersion droplet 6. The theoretical distance for the laser beam to completely image in the immersion liquid after passing through the transparent mask substrate 5 is the distance between the surface of the holographic pattern on the transparent mask substrate 5 and the imaging surface in the immersion liquid. To ensure that the imaging position of the laser beam is in the immersion droplet 6, and not inside the transparent mask substrate 5 or behind the wafer substrate, the theoretical imaging distance z of the laser beam should be greater than the thickness of the transparent mask substrate 5 and less than the sum of the maximum thickness e that the immersion droplet 6 can reach on the surface of the transparent mask substrate 5 and the thickness of the transparent mask substrate 5, so as to ensure that the laser beam can image on the photoresist layer of the wafer substrate.

[0088] To fully utilize the surface tension of the immersed droplet 6, a hydrophobic structure layer 11 is formed on the transparent mask substrate 5. The hydrophobic structure layer 11 and the holographic pattern are respectively located on opposite sides of the transparent mask substrate 5. By etching some micro- and nano-structures of the hydrophobic structure layer 11 on the back side of the transparent mask substrate 5, the adhesion between the transparent mask substrate 5 and the immersed droplet 6 is increased. By changing the position of the micro- and nano-structures within the hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, hydrophobic high-adhesion and hydrophobic low-adhesion surfaces can be achieved, such as... Figure 5 As shown. Specifically, a spherical micro-nano array structure can be etched onto the back of the transparent mask substrate 5 as a hydrophobic structure layer 11. This achieves both high adhesion to increase the thickness of the immersed droplet 6 and hydrophobicity, thereby protecting the transparent mask substrate 5.

[0089] like Figure 6As shown, a limiting groove 8 is provided on the side of the transparent mask substrate 5 facing away from the holographic pattern, and the limiting groove 8 is correspondingly positioned to the holographic pattern. A flow channel 9 is also provided on the transparent mask substrate 5. One end of the flow channel 9 is connected to the limiting groove 8, and the other end extends to the edge of the transparent mask substrate 5 and connects to the outside. A fluid-driven pump 10 is connected to the flow channel 9. In the upright exposure optical path, the flow is guided by etching the flow channel 9, allowing the immersed droplet 6 to flow accurately to the corresponding area of ​​the holographic pattern. At this time, the required amount of water can be accurately obtained by the area of ​​the holographic pattern region and the etching depth of the limiting groove 8. The immersed droplet 6 flows from the flow channel 9 on one side of the transparent mask substrate 5 into the limiting groove 8, and the size of the limiting groove 8 is constant. After calculating the theoretical imaging distance of the transparent mask substrate 5 using an algorithm, and determining the area size of the limiting groove 8 as S, the volume of the immersed droplet 6 is the product of the bottom area of ​​the limiting groove 8 and the theoretical distance. Precisely controlling the volume of the droplet entering the limiting groove 8 ensures it completely covers the groove, achieving complete immersion. After photolithography, the waste liquid flows out from the drainage channel 9 on the right side, and the residual liquid is extracted by the fluid-driven pump 10 to clean the transparent mask substrate 5.

[0090] In the upright exposure optical path, based on the current-guiding structure, some photonic crystal layers 12 micro-nano structures can be further etched on the bottom surface of the limiting groove 8 to improve the energy utilization rate of the transparent mask substrate 5 at the limiting groove 8. Specifically, such as Figure 7 As shown, the 12 micro-nano structure of the photonic crystal layer is a series of periodically arranged photonic crystal structures. The light field confinement of a specific wavelength is achieved on the photonic crystal structure to improve the energy utilization rate.

[0091] The exposure structure provided in this embodiment achieves separation of the immersion droplet 6 and the holographic pattern mask structure on the transparent mask substrate 5 by flipping the transparent mask substrate 5. This allows for complete immersion of the immersion droplet 6 into the surface of the transparent mask substrate 5, protecting the transparent mask substrate 5 and making it easier to clean the droplet on the back side of the transparent mask substrate 5 after photolithography. By calculating and setting a smaller imaging distance and utilizing the surface tension of the droplet on the transparent mask substrate 5, a smaller imaging structure size and less water consumption are achieved. By setting a hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, the maximum thickness of the immersion droplet 6 on the surface of the transparent mask substrate 5 is increased, thereby increasing the imaging distance. The limiting groove 8 and the drainage channel 9 on the surface of the transparent mask substrate 5 are used to accurately guide the immersion droplet 6 into the limiting groove 8, achieving precise immersion of the limiting groove 8. By combining the drainage structure with the micro / nano structure of the photonic crystal layer 12, the energy utilization rate of the limiting groove 8 region is improved. Once the size of the limiting groove 8 and the imaging distance are determined, the volume of liquid dripped into the limiting groove 8 can be quantitatively controlled, achieving complete immersion while saving liquid usage.

[0092] When testing the imaging quality of the exposure equipment, the transparent mask body is first fixed, and its angle is adjusted to be perpendicular to the direction of the laser beam. Then, water of the same volume as the limiting groove on the surface of the transparent mask body is injected as an immersion droplet. The wafer substrate is moved to the imaging area to find a suitable focal plane, and then the laser is activated for immersion exposure. In this embodiment, the laser wavelength is 354.776 nm, the size of the projected pattern on the transparent mask body is 1.5 mm × 1.5 mm, the aperture size on the projected pattern is 300 nm, and the minimum linewidth of the exposure pattern obtained on the wafer substrate is 350 nm. If no immersion droplet is used and imaging is performed directly in air, the minimum linewidth of the exposure pattern obtained on the wafer substrate is 450 nm. It can be seen that the minimum linewidth of the laser image is reduced after passing through the immersion droplet. As an alternative implementation, the exposure structure in this embodiment adopts an inverted structure, and the overall structure of the exposure equipment is as follows: Figure 8 As shown, the transparent mask substrate 5 is disposed above the wafer substrate. The positions of the exposure stage 7 and the mask mounting stage can be arbitrarily adjusted by utilizing the surface tension of the immersed droplets 6 on the photoresist layer surface. The surface tension of a liquid is essentially an intermolecular force. Intermolecular forces, also known as van der Waals forces, include inductive forces, dispersion forces, and orientation forces, which are naturally related to the polarity of the molecules. In this embodiment, a hydrophilic layer is disposed on the surface of the photoresist layer. The adhesion of droplets to a solid surface is related to the surface energy of the solid. On a smooth solid surface, the greater the surface energy of the solid, the more hydrophilic it is, i.e., the greater its adhesion to water. The smaller the surface energy of the solid, the more hydrophobic it is, and the weaker its adhesion to water. Hydrophilic surfaces generally have hydroxyl, carboxyl, and amino groups, while hydrophobic surfaces have fluorine, chlorine, and carbon branched groups. In the inverted structure exposure optical path, in order to better utilize the surface tension of the liquid on the surface of the photoresist layer in the inverted optical path, some treatments are performed on the surface of the photoresist layer to increase the surface tension between the droplet and the photoresist layer. Since the photolithography precision requirements on the surface of the photoresist layer cannot be used to etch some micro-nano structures, some hydrophilic treatments can be performed on the surface of the photoresist layer before exposure without affecting the photolithography process, so that its surface has hydroxyl, carboxyl, amino and other groups.

[0093] As an alternative implementation, the exposure structure in this embodiment adopts an inverted structure. The transparent mask substrate 5 is disposed above the wafer substrate, and an immersion droplet 6 is appropriately placed between the transparent mask substrate 5 and the wafer substrate. The immersion droplet 6 is adapted to be adsorbed onto the surface of the wafer substrate by surface tension. The immersion droplet and the transparent mask substrate 5 are separately disposed, so that there is a gap between the immersion droplet and the transparent mask substrate. In this case, there is no need to limit the imaging parameters of the transparent mask substrate 5. When the exposure equipment is working, the position of the wafer substrate is adjusted until the exposure beam can present a clear image on the photoresist layer of the wafer substrate, and then the position of the wafer substrate is fixed. Since the immersion droplet is in direct contact with the wafer substrate, the exposure beam, after passing through the transparent mask substrate and carrying holographic pattern information, will inevitably be imaged on the wafer substrate.

[0094] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An exposure structure, characterized by, The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method.

2. The exposure structure according to claim 1, wherein The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method.

3. The exposure structure according to claim 1 or 2, characterized by The application relates to a photolithography device and a photolithography method.

4. The exposure structure according to claim 1 or 2, characterized by The application relates to a photolithography device and a photolithography method.

5. The exposure structure according to claim 1 or 2, characterized by The application relates to a photolithography device and a photolithography method.

6. The exposure structure according to claim 5, wherein The application relates to a photolithography device and a photolithography method.

7. The exposure structure according to claim 5, wherein The application relates to a photolithography device and a photolithography method.

8. The exposure structure according to claim 5, wherein The application relates to a photolithography device and a photolithography method.

9. An exposure structure, characterized by, The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. The application relates to a photolithography device and a photolithography method. 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10. An exposure apparatus characterized by comprising: The exposure structure according to any one of claims 1 to 8 or 9, further comprising an exposure light source (1), an illumination light path (2), a mirror (3), and a mask loading stage (4), wherein the transparent mask substrate (5) is mounted on the mask loading stage (4), and the exposure light source (1) emits an exposure light beam which is sequentially subjected to light path adjustment by the illumination light path (2) and reflection by the mirror (3) and then irradiated onto the transparent mask substrate (5).

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